Commercial products based upon compositions containing thioglycolates, sulfites or alkali metal hydroxides, such as sodium hydroxides, have been widely used to permanently straighten unstraight hair, especially to straighten unstraight Negro hair. Of these products, the thioglycolate compositions and the sulfite compositions which have been commercially marketed have been relatively ineffective, with the hair in many cases reverting at least partially to the original unstraight form. While very effective in producing the desired straightening effect, sodium hydroxide compositions are very harsh to both the scalp and the hair, and the use of such compositions has resulted in numerous instances of scalp irritation and/or burning, and has also resulted in a substantial reduction of the strength of the treated hair, and even, in some instances, considerable hair loss.
Various guanidine compounds have been evaluated by the prior art in hair waving or hair straightening compositions. Of these guanidine thioglycolate appears to have had the most attention by researchers in this art. See, for example, Shansky, American Perfumer and Cosmetics, Volume 78, August, 1963, 32-34; Bogaty et al, American Perfumer and Cosmetics, Volume 78, November, 1963, pages 45-47; and Shansky, American Perfumer and Cosmetics, Volume 78, December, 1963, pages 29-30.
Various organic bases including guanidine have been found to accelerate the dehairing effect of calcium hydroxide suspensions. See, e.g. Barry, "Delipatories" Cosmetic Science and Technology, Edited by Balsam and Sagarin, 2nd Edition, Volume 2, Chapter 18, page 39, 45, Wiley Interscience, New York, 1972 and Barry "Depilatories" Cosmetic Science and Technology, Edited by Sagarin, First Edition, Chapter 20, page 461-462, Interscience Publishers, New York, 1957, and references cited therein.
The co-pending application of Mario de la Guardia, Ser. No. 805,149, filed June 9, 1977, discloses that guanidine hydroxide is an effective human hair straightening or relaxing composition, as well as an effective permanent wave composition. The compositions exhibit improved hair strength retention and significantly reduce scalp irritation, compared to hair relaxing compositions based on alkali metal hydroxides. The permanent relaxation effect is generally as good as that achieved by the use of alkali metal hydroxides (such as sodium hydroxide).
U.S. Pat. No. 3,157,578, Nov. 17, 1964, discloses compositions for the permanent waving of human hair utilizing a solution containing, e.g. thioglycollic acid and guanidine carbonate. These compositions are employed in the form of aqueous solutions having a pH value of from 7-9, with the guanidine used to replace ammonia used previously thereto, both to function as a neutralizing agent for the acid reducing agent, and also in the form of ammonium carbonate for pH control.
U.S. Pat. No. 3,861,868 of Jan. 21, 1975 acknowledges, in column 1 thereof, earlier abandoned applications relating to the use of guanidine salts in hair dying compositions and hair bleaching compositions.
British Pat. No. 1,274,565 of May 17, 1972 discloses a process for the straightening of human hair wherein the hair straightening is conducted in two separate stages. In the first stage, a known keratin softening substance, such as an alkali hydroxide, sulfite or bisulfite, or a salt of a mercaptocarboxylic acid, is permitted to act upon the hair. After the extensive removal of the keratin softening component, a media containing a swelling substance is applied to the hair. Suitable swelling agents include monovalent aliphatic alcohol, aromatic alcohols, aliphatic diols, ether alcohols, sulfoxides, sulfones, thiocyanates, thiourea and urea, and water-soluble derivatives thereof.
U.S. Pat. No. 3,865,930 of Feb. 11, 1975 discloses a permanent wave composition based on a two-stage operation, wherein in the first stage the S-S linkages of the keratin fiber are opened at an alkaline pH with the addition of a reducing agent such as a thiol. The hair is then treated in a second stage with an oxidizing or neutralizing agent to reconstitute the S-S bridges, so as to impart to the hair the desired configuration. The patent relates to a composition for the aforesaid second stage, wherein the S-S bridges are reformed. This composition is a two-component composition, with one component based on a water-soluble sulfite, bisulfite, metabisulfite or thiourea, and the other component is hydrogen peroxide.
U.S. Pat. Nos. 2,817,342 of Dec. 24, 1957 and 2,840,086 of June 24, 1958 relate to permanent waving compositions based upon sulfite-type materials. Among other acid sulfites disclosed are an acid solution of guanidine bisulfite, formed by bubbling sulfur dioxide gas into an aqueous solution of guanidine carbonate.
Japanese Pat. No. 76-9013 discloses hair waving or straightening treatments wherein the hair is initially treated with a weak alkali, followed by a treatment with a chelating metallic salt solution. Calcium oxide or calcium hydroxide is used as a chelating agent to prevent mutual interactions of the active ingredients.
U.S. Pat. No. 2,836,543 of May 27, 1954 discloses the use of guanidine as a swelling agent component in a hair setting composition. The composition also includes a water-soluble sulfite and a polyfunctional aromatic additive compound, such as genetistic acid, which acts as an accelerator.
U.S. Pat. No. 3,642,429 of Feb. 15, 1972 is directed to a hair treatment composition based on a polycondensate of methylol compounds and an urein compound. The generic formula for the urein compound appears to encompass guanidine, but guanidine is not named in that patent.
U.S. Pat. No. 3,686,296 is directed to depilatories which are nitrogen-based thioglycerol molecular complexes. The nitrogen base may be, e.g. guanidine or guanidine hydrochloride.